The Absolute Geostrophic Velocity Field and Wintertime Convection in the Japan/East Sea Estimated from an Array of Profiling Floats S. Riser (University of Washington, USA) M. Danchenkov (FERHRI, Vladivostok, Russia) K. Kim (Seoul National University, Korea) J-H Yoon (Kyushu University, Japan)

The Japan/East Sea is over 3000 m deep and is connected to the N The Japan/East Sea is over 3000 m deep and is connected to the N. Pacific and Okhotsk Sea via several sills that are < 150 m deep. Summer winds: S, SW Winter winds: NW Cold winter winds create conditions for strong air-sea interaction

In 1999 an array of 35 profiling floats were deployed in the Japan/East Sea for purposes of studying circulation in the northern portion of the Sea, especially in winter. Parking depth = 800 m t = 7 days Note: a great deal of international cooperation was required to accomplish this!

These were the first deployments of APEX floats These were the first deployments of APEX floats. Most of the floats worked well for 2 years or more, and some continue to work over 4 years after deployment.

Since August 1999 nearly 7000 profiles of T and S have been collected. 8/99 – 11/03

T (C) @ 5 m estimated from floats, 1/2000 MLD (m) estimated from floats, 1/2000

Estimation of absolute geostrophic velocity: 0-800 dynamic ht (from T and S) 800 m p from float drifts

By combining the maps of absolute geostrophic velocity at 800 m inferred from the float drifts, and the dynamic height map at any level above 800 m inferred from measured T and S profiles, we can determine the absolute geostrophic velocity at any level above 800 m (speeds 1-10 cm/sec) 200 m absolute geostrophic flow, 1999-2002

Seasonal maps of absolute geostrophic flow at the sea surface

Summer Winter There is strong seasonal variability above 150 m; below this level T and S are nearly homogeneous.

Summer Winter In the western part of the Sea, off the coast of Russia, deep convection occurs in winter (variable year-to-year).

2/18/01   10/25/00 Wintertime convection can be seen in the evolution of the potential density profile between 10/2000 and 2/2001.

T (C) Temperature profiles from Float 230, August 1999 – September 2002, showing wintertime deep convection

All winter convection profiles, 1999-2003, shown on winter absolute geostrophic velocity map

Results: Profiling floats can be used to estimate the absolute velocity field when the spatial resolution is adequate. Profiling floats are an excellent tool for examining wintertime air-sea interaction. In the case of the Japan/East Sea, convection in the western portion of the Sea is consistent with 400 watts/m2 over most of the winter. There are implications to long-term changes that are taking place in the deep waters of the Japan East Sea.